Current Question

Hello

Doing some training at the moment and am confused. I have a friend who touched a live wire at the ceiling whilst fitting a rose, without turning off the power. When he touched it with his finger he said he felt it heat up and then pulled it away, like touching a hot kettle. He said he felt a rushing sensation through his arm and chest, but is unsure if this was panic upon realising what had happened, or some kind of shock. He also said that when he went to turn off the power the RCD had tripped, which it is set to at 30mA. He was standing on stepladders with plastic sheets and bare feet, and holding an insulated screwdriver and a metal plate one the other hand. He felt fine and went to the doctor and had full check up, neurological test and ECG and is fine, has no entry burn but what looks like a burn at his elbow that he realised a few days later, but I don’t think it’s related as it looks like a superficial friction burn.

My confusion lies here:

1. If the RCD tripped, surely that means that 30mA current was received, why is he absolutely fine? I thought a current of this range would cause at least some pain, whereas the symptoms he describes are akin to a 1mA current.

2. I think the voltage was 230V as it is in Scotland, if he felt heat why would there be no burns, especially if there was a large current. The burn at his elbow can’t be an exit point, as it is not a path to ground, can it?

3.  Did the fact that he was standing on a plastic sheet mean that there was no path to ground, and that there was no shock at all and he only felt heat on the fingertip?

Im obviously glad he is ok! I have also sternly told him how lucky he is and to never attempt anything unless he knows what he is doing. I am just a little confused, apologies if this is obvious, I have just started my training.

Thank you!

Sounds like a normal electric shock. Contrary to popular belief you don't die instantly.

The RCD did it's job and cut off the supply before any real harm was done. A good example of why they are fitted and a good example why you isolate a circuit and test that it is actually dead before touching it. You would only get a physical burn if the shock lasted longer than it did.

It's 230V (usually more like 240) in Scotland, the same as the rest of the UK

This does remind me of a situation I once encountered on visiting a friend's house some years ago. He had been decorating, and to finish off he shampooed he carpet.

As I arrived he was about to reinstate a ceiling light fitting.

So, there he is, shoes off  and socks damp from the carpet, standing on an aluminium ladder and about to start  reconnecting !  And no, he had not cut the power. This was before RCD were common too.

Thanks for replies! Makes sense I guess that RCDs are there to stop serious harm, like in this case.